Hi Eric,
These are the settings I would use for a good all-round mount of Google Drive on Windows with 5GB available for caching:
rclone mount --network-mode --buffer-size=0 --vfs-cache-mode=full --vfs-cache-max-age=168h --vfs-cache-max-size=5G --drive-pacer-min-sleep=10ms --drive-pacer-burst=200 --cache-dir c:\temps plsmain: c:\test
I think it will fine for Plex too, so I suggest you try it and let me know how it compares to the commands you already tried.
The settings are inspired by these forum posts:
https://forum.rclone.org/t/for-mount-sftp-why-right-click-on-exe-file-is-so-slow-until-it-freezes/33830/46
https://forum.rclone.org/t/understanding-drive-pacer-burst-google-drive/32917/3